In a liquid crystal display device, liquid crystal is a substance that does not itself illuminate light. Instead, the liquid crystal relies on reflecting light from a light source, thereby displaying images and data. In the case of a typical liquid crystal display device, a backlight module powered by electricity supplies the needed light.
Generally, backlight modules can be classified into an edge lighting type or a bottom lighting type based upon the location of lamps within the device. The edge lighting type backlight module has a lamp unit arranged at a side portion of a light guiding plate that guides light. The edge lighting type backlight modules are commonly employed in small-sized LCD due to their lightweight, small size, and low electric consumption. However, the edge lighting type backlight modules are not suitable for large-sized LCD (20 inches or more). A bottom lighting type backlight module has a plurality of lamps arranged in regular positions to directly illuminate an entire surface of an LCD panel. The bottom lighting type backlight modules have higher efficiency of light usage and longer operational lifetime than the edge lighting type backlight modules, the bottom lighting type backlight modules are especially used in large-sized LCD devices. However, an LCD device usually employs a significant amount of lamps to reach a high luminance. The significant amount of lamps results in a great deal of heat produced and cumulated inside the LCD device. Therefore, heat dissipation of the direct type backlight modules is usually a hard nut to crack.
Referring to FIG. 5, a typical lamp-fixing device 10 used for fixing lamp tubes in backlight module is shown. The lamp-fixing device 10 includes two same side-plates 11, a number of fixing holes 111, and a number of heat dissipation holes 112. The fixing holes 111 are aligned in each side-plate 11, and are used for receiving ends of lamp tubes 12. The heat dissipation holes 112 are defined in each side-plate 11 adjacent to the fixing holes 111. The two side plates 11 are disposed apart, and collectively fixing the two ends of the lamp tubes 12.
However, because the ends of the lamp tubes 12 are hold in the fixing holes 111, heat substantially produced from the ends of the lamp tubes 12 is not easily dissipated, even though the heat dissipation holes 112 are defined aside the fixing holes 111. In addition, dust may pass through the heat dissipation holes 112 to adhere to the surface of lamp tubes 12 or to optical sheets (not shown) and disposes thereon, thus deteriorating the brightness of the backlight module using the lamp-fixing device 10. Furthermore, because the ends of the light tubes 12 are inserted into side-plates 11, the lamp-fixing device 10 and the lamp tubes 12 need to be disassembled whenever any lamp tubes 12 are damaged. Disassembling the lamp-fixing device 10 is very troublesome and also increases the risk of damaging other good lamp tubes 12 of the lamp-fixing device 10.
What is needed, therefore, is a lamp-fixing device and a backlight module using the same that overcome the above mentioned disadvantage.